1. Field of the Invention
The present invention relates to a fabric-based sensor for monitoring vital signs or other electrical impulses of a subject. The sensor is woven or knitted from conductive fibers and, when in contact with the body, is capable of receiving signals from the wearer and transmitting them to a processing or monitoring device through a data-output connection or terminal. The sensor may be integrated into a garment or used as independently as a conductive patch, and it may provide bi-directional communication by sending electrical impulses back to the subject.
2. Background of the Art
Conventional medical electrodes are used for sensing electrical transmission between the surface of a subject's skin and electrical leads connected to monitoring equipment. Typically, the electrodes use an adhesive backing to affix the conductive lead to the subject's skin. A conductive gel is often used to enhance electrical transmission.
Many of the existing sensors are either rubberized electrodes or gel-based sensors that stick to the body of the subject. Both types of sensors have the major drawbacks of being difficult to remove and causing skin irritation and chafing.
U.S. Pat. Nos. 4,722,354 and 5,450,845 to Axelgaard describe an electrical stimulation electrode which integrates conductive fibers with pre-wired, hard-wired electrical leads into a flexible electrode patch. The flexible patch allows for greater patient comfort and movement, without disruption of the electrode placement. The patch described by Axelgaard consists of several layers, including a non-conductive layer, an adhesive layer and the conductive fiber layer.
Co-pending application U.S. Ser. No. 09/157,607, filed on Sep. 21, 1998, now U.S. Pat. No. 6,145,551 to Jayaraman, et al., incorporated herein by reference in its entirety as if fully set forth herein, discloses a process for the production of a woven garment which can accommodate armholes and which may also incorporate conductive fibers integrated into the woven fabric by one weaving process. The garment produced by the Jayaraman process is capable of collecting data from several different types of sensors attached thereto, and transmitting the data through a single connector, such as a snap T-connector.
Additionally, co-pending application U.S. Ser. No. 09/273,175, filed on Mar. 19, 1999 by Jayaraman et al., now U.S. Pat. No. 6,381,482, and incorporated by reference in its entirety as if fully set forth herein, discloses a fabric or garment which includes an integrated information infrastructure for collecting, processing, transmitting and receiving information. The garment functions as a “wearable motherboard,” which, by utilizing the interconnection of electrical conductive fibers, integrates many data-collecting sensors into the garment without the need for multiple stand-alone wires or cables. The information may be transmitted to several monitoring devices through a single electronic lead or transceiver.
There exists a need in the art for a flexible electrode which can adhere to the subject without the need for pain-causing adhesive. The present invention is directed to a conductive fabric sensor which does not include multiple layers such as the Axelgaard electrode and, when in contact with the body, picks up electrical signals from the wearer. Utilizing the weaving technique and the interconnection of electrical conductive fibers of the co-pending Jayaraman application and the Jayaraman patent, it is possible to produce a comfortable fabric-based sensor which is very light weight and does not require hard wiring or adhesives.